"ARE WE TALKING ABOUT THE SAME COLOR?"

There are differences in value of some colors between brands of paint. Even though the same pigments are used, some manufacturers may use more or less pigment in their formula, or use a finer or coarser grind of pigment; all will make some difference in the intensity of the color. Some colors that are themselves mixtures, such as Payne's Gray, may vary greatly in the proportions of the pigments used - ultramarine blue and black in this case - resulting in a significant variation of color. Most differences are small enough to ignore, but a few are significant enough to warn you: If you are following someone else's mixing instructions, try to use the brands mentioned. Don't panic and think I'm suggesting that you need a tube of every burnt sienna ever made. As I said, most times the differences are slight enough that minor adjustments will yield the desired result. Being aware of this, however, is one more tool to aid you in troubleshooting your mixtures.

I've given some examples below comparing colors of different brands. No, I don't have a drawer full of every burnt sienna ever made. What I do have are sample swatches taken from other artists who use different brands than I do. I carry around a package of 3/4" round, white self adhesive labels. These can be found in the office supply section of most variety stores. I paint a sample "dot" and note the color and brand. When I get back to my studio, I stick the sample on an index card that contains other examples of the same color - including the brand that I prefer, Golden Acrylic (both High Load and Fluid Matte varieties) - and note the brand underneath. To keep them from being scattered to the Four Directions, I store them in a photo album that accepts 4"x6" photos. See the illustration below for how my reference cards are set up. I would recommend you make your own color charts for comparison rather than comparing the color cards that the manufacturers distribute. These are fine for showing the range of colors available, but due to the limitations of printing, they're not reliable for accurate comparison.

FIGURE 9. There's a large disparity between these two Payne's Grays, with the JoSonja being more blue. The two pigments making up this color are Ivory Black (PBk 7) and Ultramarine Blue (PB 29). Incidentally, you can make this mixture yourself.

FIGURE 10. Notice that the JoSonja's version appears more turquoise. I don't use this in any mix requiring Ultramarine Blue. The JoSonja's version, called simply, "Ultramarine", is a formulation of Ultramarine Blue (PB 29), Pthalo Blue Green Shade (PB 15:4) and Titanium White (PW 6). These are the very same pigments that make up their "Cobalt Blue Hue", by the way, just in different proportions. I don't know why this color is formulated this way.
Jo Sonja's "true" Ultramarine Blue is called "Ultra Blue Deep" and contains nothing but the PB 29 pigment. If you use this in some mixes, you will get colors insanely biased towards blue or an unexpected green bias due to the Pthalo Blue in the formula. Pthalo colors are incredibly strong colors, and easily overpower any mix they're used in. I love them, but they have their place, and this isn't one of them.

FIGURE 11. No discernible differences between the Grumbacher and Golden Cerulean Blue. But the Pebeo brand is slightly bluer. This is a perfect example of buying your color buy the C.I.N. and NOT the color name. Pebeo calls this color Cerulean blue, but the C.I.N. is PB 28 - the C.I.N. for Cobalt Blue.

FIGURE 12. There are some differences here. Grumbacher is slightly more yellow. Also, there are differences in the opacity, JoSonja's being the most opaque.